Field of the Invention
The present invention relates to a solid state imaging device and a method of driving the solid state imaging device.
Description of the Related Art
A solid state imaging device including an analog-digital converter is known (refer to, for example, Japanese Laid-Open Patent Publication No. 2008-098722 (Patent Reference 1)). As for a pixel array unit, unit pixels each including a photoelectric conversion element are two-dimensionally arranged in a matrix form, and a column signal line is wired every column in the matrix arrangement of the unit pixels. A row scanning unit selects and controls respective unit pixels in the pixel array unit every row. The analog-digital converter converts an analog signal output from a unit pixel in the row selected and controlled by the row scanning unit via the column signal line to a digital signal. The analog-digital converter includes a first comparison unit, a second comparison unit, and a counting unit. The first comparison unit compares the analog signal with any one of a plurality of first reference voltages taking a slope shape and having inclinations which are identical with each other. The second comparison unit compares a second reference voltage which is different from the first reference voltage in slope inclination with any one of the plurality of the first reference voltages used in the first comparison unit. The counting unit conducts count operation with a count quantity depending upon comparison results in the first and second comparison units, and converts a count value to the digital signal.